Solution:
Given that a medical researcher needs 6 people to test the effectiveness of an experimental drug. If 13 people have volunteered for the test, this implies that
[tex]\begin{gathered} total\text{ number of options in the set = 13} \\ number\text{ of oprions to be chosen = 6} \end{gathered}[/tex]
To evaluate the number of people that can be selected, we use the combination formula expressed as
In this case,
[tex]\begin{gathered} n=13 \\ r=6 \end{gathered}[/tex]
Thus, the question involves combination.
